Recent remarkable development of magnetic recording technologies has provided large-capacity drives with magnetic recording media having higher recording densities. However, longitudinal magnetic recording media widely used at present need small recording bits and thus high coercivity to such extent that recording cannot be conducted by magnetic heads, to have higher magnetic recording density. To solve these problems, perpendicular magnetic recording with high recording density has been researched.
Perpendicular magnetic recording is conducted on a recording medium whose magnetic film has a magnetization easy-axis vertical to its surface, with a small demagnetizing field in bits and little deterioration of read-write characteristics even at an increased recording density, thus suitable for a high magnetic recording density. Developed for the perpendicular magnetic recording is a double-layer recording medium with high recording sensitivity, which comprises a magnetic recording film and a soft magnetic film.
As the soft magnetic film for the double-layer recording medium, soft magnetic Co alloy films were proposed by JP 08-014889 B and JP 09-282656 A.
The formation of the soft magnetic films in the double layer media described in JP 08-014889 B and JP 09-282656 A is generally conducted by a magnetron sputtering method. The magnetron sputtering method comprises causing a magnetic flux to leak onto a target surface with a magnet disposed on the rear side of a target, and concentrating plasma in a region of the leaked magnetic flux to form a thin film at a high speed. Because the unevenness of crystal orientation and metal structure of a magnetic target leads to the unevenness of the leaked magnetic flux and thus the unevenness of a sputtered film in the magnetron sputtering method, it is important to develop a target with little unevenness. In the sputtering method, dust called particles is generated from the target during sputtering. It is thus important to suppress the generation of particles. Because there is an extremely brittle intermetallic compound phase, which tends to constitute the particles, particularly in the Co alloy target containing Zr, Nb, Ta, etc., it is extremely important to control the shape and distribution of the intermetallic compound phase.
Because Zr is not substantially dissolved in Co, brittle intermetallic compounds are formed even if Zr is added in a small amount. Accordingly, it is extremely important to control the structure of a Zr-containing Co alloy.